The present invention relates no a connection arrangement for monitoring fetal heart rate. The arrangement electrically interconnects a remote fetal monitoring device with bipolar fetal electrodes.
U.S. Pat. No. Re 28,990, which is incorporated herein by reference, discloses the bipolar fetal electrode assembly commonly used to monitor fetal heart rate during birth. In use of that assembly, a doctor inserts the forward end of a curved guide tube through the mother's vagina and cervix until the forward end of the guide tube makes contact with the fetal head or other portion of the fetus. Holding the forward end of the guide tube stationary, the doctor then pushes the rear end of a flexible driving tube forwardly until a spiral fetal electrode at the forward end of one wire of a twisted wire pair makes contact with the fetal epidermis. The forward end of the other wire has a spade-like maternal electrode which is electrically isolated from the spiral fetal electrode.
The doctor then rotates the flexible driving tube clockwise about one full turn while maintaining the forward end of the guide tube against the fetal head. This will screw spiral electrode into the fetal epidermis. Thereafter, the doctor removes his fingers from the mother's vagina, grasps the outer ends of the driving tube and the guide tube, and slides these tubes as a unit off the wires, leaving only the bipolar electrodes and the two twisted wires within the mother.
The outer ends of the wires are then connected to a suitable apparatus for monitoring fetal heart rate. Such an apparatus is discussed in U.S. Pat. No. 4,632,121, the contents of which are also incorporated by reference and which also shows a cable assembly for effecting electrical connection between the electrodes and the fetal monitor. A galvanic potential difference may then be measured between the bipolar electrodes. The wires connected to the electrodes are twisted about each other so that any induced voltages caused by external electromagnetic interference will be the same in each and therefore will not adversely affect the measurement of the galvanic potential difference between the electrodes.
In practice, the ends of the twisted wires are left uninsulated, e.g. by as much as 5/8 inch to 3/4 inch, to allow connection to the monitor and to enable removal of the guide and driving tubes from the twisted wires.
Manually connecting the uninsulated ends of the twisted wire pair to the base plate is somewhat cumbersome and creates the possibility that the wires may unintentionally short each other. If shorted, the wires will be unable to transmit correct signals from the fetal electrodes.
It would therefore be desirable to effect electrical interconnection between the fetal and maternal electrodes and a remote fetal monitoring device without handling uninsulated ends of wires.